1. Field of the Invention
The description is concerned with nonvolatile semiconductor memory devices, in particular to a nonvolatile semiconductor memory device having a wired-OR structure.
2. Discussion of Related Art
Generally, a nonvolatile semiconductor memory device may use a wired-OR circuit for a verifying operation to find defects in programmed data. For example, in a nonvolatile semiconductor memory device having a cache function, it is possible to highly improve the operation by using a wired-OR scheme that verifies programmed data of several memory cells all together, not in a Y-scanning scheme that verifies programmed data one by one.
However, in such a nonvolatile semiconductor memory device, there may be defects from memory cells, bitlines, or page buffers that temporarily store data read out from memory cells. The defects located in memory cells or bitlines may be cured by way of column repair. In other words, if there is an address designating memory cells or bitlines including a defect in a nonvolatile semiconductor memory device that has a column repair scheme, the data may be redirected toward a spare memory cell or bitline. Thus, the defective memory cell or bitline is repaired.
In contrast, it is practically impossible for a nonvolatile semiconductor memory device, which has defects in the page buffers in themselves, to be repaired completely using the column repair method. That is, although a defective page buffer is substituted with a spare page buffer by means of the column repair scheme, it is impossible to execute a verifying operation with the proper wired-OR scheme when a data arises from the defective page buffer. Therefore, in order to conduct an appropriate wired-OR verifying operation, a nonvolatile semiconductor memory device is required of having a structure capable of blocking data transmission from a defective page buffer, in addition to a column repair circuit that substitutes a defective page buffer with a spare page buffer.